Lock-out party-line telephone system.



PATENTED MAR. 10, 1903.

No. 722,362. v

G. L. GOODRUM & J. W. LATTIG.

LOCK-OUT PARTY LINE TELEPHONE SYSTEM.

APPLICATION FILED SEPT. 12, 1902. no MODEL.

l hyywl lll l l lglllw UNITED STATES PATENT EEICE.

CHARLES LANE GQODRUM AND JACOB WILLIAM LATTIG, OF PHILADELPHIA, PENNSYLVANIA.

LOCK-OUT PARTY-LINE TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent NO. 722,362, dated March 10, 1903.

Application filed September 12, 1902. Serial No. 123,065. (No model.)

To aZZ whom it ntay concern.-

Be it known that we, CHARLES LANE GOOD- RUM and JACOB WILLIAM LATTIG, citizens of the United States. residing at Philadelphia,

in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Lock-Out Party-Line Telephone Systems; and we (lohereby declare the following to be a full, clear, and exact dexo scription of the invention, such as will enable -others skilled in the art to which it appertains to make and use the same.

Our invention relates to telephone systems, and particularly to those systems wherein I 5 more than one subscribers station is connected to the same line. Suchaline is commonly known as a party-line.

Our invention has for its object the prod uction of aparty-line system such that when the line is in use by one party the other parties whose telephone sets are in connection therewith can neither listen in nor call central or each other until the linebe again idle. In the operation of the system we provide for an exception when it is desired to permit two subscribers on the same line to converse. In such case a specific action on the part of an operator at the central office or its equivalent is required, and in every case a call must first be made to the central office before communication can be had over the line. Such systems are usually designated lock-out partyline systems, and our apparatus is designed to work with centralized or common battery. As will appear, however, it can be adapted to other than common-battery systems, and it will work equally well where selective or non-selective signaling is employed.

Our invention consists, essentially, in the employment at each subscribers station of a mechanical lock for the switch, a polarized controlling-magnet therefor having a biased armature normally set to locking position, to-' gether with means to connect this magnet to one side of the line in initiating a call, so that it will thereupon unlock the switch if the line is idle, but retain it locked if the line is busy. WVe provide a source of energy connected across the line and divided in such 50 fashion that normally the side of line above referred to will be at such apotential and receive such a polarity as to insure the proper operation of the first locking device brought into connection with the line by a calling subscriber; but after such subscriber shall have secured possession of the line the bridging of his telephone set thereacross will cause a reversal of the polarity, so that any locking devices thereafter brought into connection with the line will remain in locking position. When one party has called and thus obtained exclusive control of the line, if it is desired to permit another party to come in we provide means whereby the polarity of current on the line may be momentarily reversed by the operator.

As an incident to the operation of our looking apparatus a visual indicator is actuated at each station to display the alternative indications of Busy or O. K. Any other desired legends may be substituted for these, or the indicator may be dispensed with. We find it useful, however.

Referring to the accompanying drawing, the figure is a diagram of a subscribers line having three stations upon it, together with portions of the apparatus at the central station and the line-terminal and signaling devices.

Referring to the drawing, A indicates the central office, in which terminate the line- 'wires 1 2 of a metallic circuit connected to subscribers apparatus at the stations B, O, and D.

The system which we have chosen to illustral-e is that described and claimed in our copending application, Serial No. 123,064, filed September 12, 1902. We willtherefore describe only so much of that system as is essential to the operation of our present invention.

The line-circuit l 2 terminates at the central office in aspring-jack J, having springs jj and a test-ringj From the conductor 1 a wire 3 is led to the line-relay g, whence a 5 wire 5 passes to an impedance-coil, from which a Wire 6 passes to the negative side of the main battery M. From the other side of this battery wire 7 is led to the impedance-coil h, and thence wire 8 passes to the line-wire 2. When a subscriber calls, a bridge is closed across the line-wires and current passing through the relay g causes it to attract its armature and close the circuit of the signallampvl. ber of pairs of connecting-plugsP P, the pair shown being connected by the cord conductors 9, 10, 11, and 12, the continuity of these conductors being interrupted by the condensers c c. From the conductor 11 a wire 13 is led ofi to the relay R, connected on its other sideby the wire 15 to ground. Similarly from the conductor 12 wire 14 passes to the relay R, and thence by wire 15 toground.

These two relays control local circuits containing the lamps r r, respectivelyrconstituting supervisory signals, and each relay responds only to current in the line with which its plug is connected. The battery M, being connected to one side of the line-circuit by wires 7 and 8 and to the other side by wires 4, 5, and 6, is in a bridge of the line. We ground this battery at a point intermediate between its terminals and nearer to one terminal than the other, so that, for instance, the number of cells between the grounded point and the positive terminal will be sufficient to give a difference of potential of ten volts, while those between the grounded pointand the negative terminal will give twenty volts. The positive terminal being connected to line-wire 2 the potential difference between that wire and the ground will be +10, while that between wire 1 and the ground will be 20. The purpose of this will appear later.

In answering a call the operator inserts plug P into jack J, and the tip of the plug thereupon passes between the springs j j, whereby a shunt 4: is'closed around the winding of the relay-magnet g, permitting the armature to fall oif and the light 2' to become extinguished.

Referring now to the apparatus at the subscribers station, as this is the same in each station we will describe that at station E for all. Here the subscribers switch is shown at S, locked in its depressed position by means of a pawl 0 pivoted to swing over a projecting piece or shoulder s on the switch-hook. The switch S has a tendency to move upward under the influence of a leaf-spring s, and in such motion a post 8 on the switch presses together a pair of spring-contacts s before the pawl stops the rise. These contacts 8 are connected on one side by wires 28 and 17 to the line-wire 2 and on the other side to the windings of a polarized electromagnet 0, from which the wires 26 and 25 pass to ground. The armature 0 of this magnet is pivoted at its middle point and is there provided with an extended arm 0, whose end passes between a pair of lugs 0 on the side of the pawl 0 The armature o is given a permanent bias to the right by means of the spring 0 so that the pawl normally stands in looking position with respect to the switch-lever. WVhen the switchhook is down, there is no circuit through wires 1 and 2, the ringer Q being included in a cir- The operatoris provided with a num-.

out from line-wire 1 by wires 18 23 2 k 25 to ground. When the switch-hook S rises after being released by the pawl or dog 0 an arm 3, rigidly fixed thereon, presses a spring .9 against a pair of contact-points to close the talking-circuit through wires 19, 20, and 21, transmitter T, and receiver T, the talking set then being bridged across the line-wires 1 2.

It will be observed that the battery M is connected on the positive side to line-wire 2 through the high-resistance impedance-coil h and on the negative side to the line-wire 1 through the corresponding impedance-coil h. It will be explained presently how the polarity on line-wire 2 is reversed by bridging any of the telephone sets across the metallic circuit. A reversal of this change is brought about when desired by the operator at the central office by establishing a short circuit around the impedancecoil h. In order to facilitate the reading of the drawing, we have shownthis short circuit in full lines as comprising the wires 16, connected at the two sides of the coil to the conductors 7 and 8 and closed together by the key K. The real position of this key and its connections would in practice be as shown in the dotted lines in each cord-circuit, the wire 16 then extending from conductor 7 on the positive side of the battery to conductor 13 through key K, and the connection then being completed to linewire 2 through the cord conductor 11, the sleeve of the plug P, and the jack-thimblej The operation of our system will now be understood. Suppose that the subscriber at station 13 desires a connection with some other subscriber not on his own line. He calls, as usual, by removing the receiver T from the hook-switch S, whereupon the latter rises. At the beginning of its upward progress the post .9 presses the springs 3 together, completing the following circuit: from ground at the central office to the in termediate point of the main battery M, from the positive terminal thereof through conductor 7, impedance-coil 72,, and conductor 8 to linewire 2, by wire 17 and wire 28 to springs 8 by wire 27 to magnet O, and by wires 26 and 25 to ground. Current flowing over this circuit with an electromotive force of ten volts is of the proper direction and of sufficient strength to energize the magnet 0, so as to throw over its armature 0 against the spring 0, the arm 0 being thereby moved to the right, carrying the dog 0 out of the path of the shoulder s on the hook-lever S and permitting the latter to rise to its fullest extent, so that at the end of its progress the arm 3 will force the spring 8 against its contact-points to close the talking-circuit in bridge across the lin e-wires, as previously set forth. The moment the talking set has been bridged across the metallic circuit the polarity of line-wire 2 is changed, and instead of having a potential difference from the earth of +10 it now has a potential difierence of 10; This is because a path has been closed from the ground at central through the twenty-volt side of the main battery and from the negative terminal thereof through conductor 6 to line-wire 1, and .thence by wires 18, 22, 21, 20, 19, and 17 to line-wire 2. The primary potential difference by the first path between the earth and line-wire 2 being +10 and the secondary potential difference being -20, the resultant is of course their algebraic sum, or 10. Thus from the instant a subscriber calls, the line being previously idle, a reversal of conditions obtain without any special act whatever on the part of either subscriber or operator. The circuit having been closed, as described, at the subscribers station, current flowing through the coils of the relay 9 will energize the latter and cause its armature to be attracted to close the circuit of the lamp 7). The operator inserts the answering-plug P in answer to the call, thereby short-circuiting the relay g and retiring the signal. The subscriber wanted being on another line, the connection is then completed in the usual way, the relays R R enabling the operator to supervise the connection. When the subscribers have finished talking, they hang up their receivers, displaying the signals 0" 1", and the operator clears out. If after the subscriber B has called and during the connection referred to either of the subscribers C or D desire to use the line, they may-attempt to call, and their switch-hooks will rise far enough to close together the contacts 8 but can rise no farther, for the reason that when the circuit of the magnet O is thus completed in each case the polarity of the current flowing therein will be such as to maintain the armature in its biased position, reinforcing the spring 0 and keeping the pawl or dog 0 in its locking position over the shoulder 3 In rising to this first position each switch-hook will bring its attached target N into such position as to display the word Busy through the opening n in the face of the containing-case. This target is shown at station 0, being omitted at the other stations, so that the circuits may be more clearly traced. It consists, essentially, of a disk or plate N, bearing on its face the two inscriptions Busy and O. K. The disk is carried on a stem 7, having an overturned end which extends through an orifice in the hook-lever S, being secured therein by the set-screw m. This construction enables the disk to be adjusted in its position relative to the switch-hook by simply turning it upon the stem end as upon a pivot, thus compensating for slight irregularities in the positioning of the mechanism in the box. In case the calling subscriber is unable to gain connection with the line the word Busy will be displayed, as stated; but if the con nection is obtained the hook-lever of course rises to its limit and carries the disk with it a sufficient distance to display the sign 0. K. Supposing that the subscriber wanted is another subscriber on the same line, subscriber B having called the operator can call the desired station in the usual way; but since the potential of line-wire 2 is such as to lock out all other talking sets than that of the calling station it is necessary to overcome this potential in order topermit the wanted subscriber to answer. This is accomplished by means of the unlocking-key K. When the operator desires another subscriber to come in on the line, she depresses the key K, and thereby short-circuits the impedance-coil 71. Now while we have spoken of the potential of the two sides of line as being that of the terminals of the battery measured from the ground nevertheless there will be in practice a considerable drop on each side due to the introduction of the coils g and it. Thus when the coil h, which may be of, say, two hundred ohms resistance is shunted by a conductor of practically no resistance there is a rise of potential on line-wire 2 from the positive pole of the battery which once more reverses the polarities, so that when the called subscriber removes his receiver from the hook the latter is at once unlocked and permitted to rise to close his talking-circuit.

It will be observed that the ground connection to line through each magnet O is but momentary. Hence it does not interfere with other connections in any system. The subscribers cannot call each other, and if they could they could not answer except as permitted by the operator at central. Consequently by bridging a battery or other source of electromotive forces across magneto lines our lock-out devices may be used thereon. Moreover, it is not necessary that the station A should be a central office. Any point on the line may be selected for the lock-out battery and unlocking-key. Thus on long farmers lines and other lines of like nature,where most of the business is between parties on the same line, eavesdropping can be prevented and an accurate record kept of all calls by an attendant at the point where the main battery may be located.

We consider our invention in its broadest aspect to include other than mechanical means for looking out. We consider all such to be within the scope and purview of our invention.

- What we claim, and desire to secure by Letters Patent of the United States, is

1. In a party-line telephone system, a linecircuit, a plurality of stations thereon, a telephone and a switching device! together with a polarized controlling device therefor, at each station, a common means for supplying current to the line, and means at each station to control the polarity or direction of the current.

2. In a telephone party-line system, a metallic line-circuit, a plurality of stations thereon, receiving and transmitting apparatus, to gether with polarized controlling means, at each station, an electric-current supply for the two sides of line such that they are main tained at opposite potentials, connections of line, and means at each station to cross the two sides of line together.

8. In a telephone party-line system, a metallic circuit and a plurality of stations thereon, a telephone, a switch, and a polarized electromagnet-controlling device therefor, at each station, means controlled by the switch to bring the controlling device into operative relation with one side of the line and a current-supply for that side of line whereby the controlling device will permit the switch thereupon to connect the telephone to line, a source of current-supply maintaining the other side of line at an opposite potential, whereby when the telephone is switched across the line a reversed current is supplied to lock the switches at all other stations.

4. In a telephone party-line system, a metallic circuit, and a plurality of stations thereon, a telephone, a switch adapted toconnect the sameacross the line, and a polarized magnetic device normally preventing such action, at each station, means for maintaining the two sides of line at opposite potentials, one greater than the other, and means operated by each switch in its action to first connect its own controlling device to permit its operation, and thereafter by connecting the telephone across the circuit to reverse the polarity of current available for the controlling devices at other stations.

5. In a telephone party-line system, a metallic circuit and a pluralityof stations thereon, a telephone, aswitch to connect the same across the line, and a polarized locking device for the switch, at each station, a battery bridged across the line and having an intermediate ground connection so placed as to give the two sides of line "opposite and unequal potentials, means actuated by each switch to connect its lockin g magnet between ground and the side of line of lower potential, whereby the device acts to unlock, and thereafter, by connecting the telephone across the line to reverse the potential on that side, whereby the switches at other stations will remain locked.

6. In a telephone party-line system, alinecircuit and a plurality of stations thereon, a telephone, a switch, and a polarized electromagnetic locking device therefor at each station, means for supplying current of one direction to line normally, to unlock the switch of a calling-station, and means to reverse said current direction by the use of the teleis reversed by the action of said calling-station and similar connection at other stations prevented.

8. In atelephone party-line system, a linecircuit and a plurality of stations thereon, a

telephone, a switch and a polarized controlling-magnet therefor at each station, means for supplying current of one direction to line normally to permit the connection of the telephone at a calling-station, means at such station to reverse the direction of current to prevent the connection of the telephones at other stations, together with means to again reverse the current to permit another telephone to be connected.

9. In a telephone party-line system, a metallic line-circuit terminating at a central office, and a plurality of subscribers stations located at different points along said circuit, a main battery at the central office bridged across the circuit, and having an intermediate point grounded, so that the potentials of the two sides of line will be different, measured from ground, a switch S at each substation adapted to be actuated to bridge a telephone transmitter and receiver across the circuit, a detent normally restricting the movement of the switch, a polarized magnet controlling said detent, a circuit-closer actuated at the beginning of movement of the switch to connect said polarized magnet to the lowpotential side of line, whereby said magnet will release the switch and permit its further movement to bridge the talking set across the circuit, so that by the balancing of potentials a reversed electromotive force will be impressed upon the line on the low side, and thereafter any switches at substations that are attempted to be actuated will remain locked by reason of the non-actuation of their polarized electromagnets when brought into connection with the line.

10. In a telephone party-line system, a pair of line-wires 1, 2, sources of current-supply therefor such that their potentials are relatively reversed, and that of line-wire 1 is higher than that of wire 2, a plurality of substations, means at each substation to bridge a telephone set across the line-wires, together with a polarized magnet normally preventing such action and adapted to be brought into connection with and to be energized bycurrent over line-wire 2, if the line is idle, but to remain inactive if the line is already bridged, together with means to temporarily raise the normal potential of line-wire 2, to permit the connection of more than one telephone to the line.

11. In a telephone party-line system a metallic line-circuit and a plurality of stations thereon, a central station, a source of currentsupply for each side of the line at the central station connected through a resistance-coil in such manner as to give the two sides opposite and unequal potentials, a magnetically-controlled switching mechanism at each substa tion adapted to be brought into connection ICO with the low-potential side of line and thereto again reverse while the coil remains shortnpon to be operated to connect its telephone circnited, to permit telephones other than the set to line, means at each station to reverse first to be connected.

the potential of the low side of line by such In testimony whereof we affix our signa- 5 connection, whereby the switching devices at tures in presence of two witnesses.

other stations will be prevented from operat- CHARLES LANE GOODRUM. ing while the line is in use, and means at the J. WILLIAM LATTIG.

central station to short-circuit the resistance- Witnesses:

coil between the low side of line and battery, MARY C. MCCARTHY,

to whereupon its initial potential will be raised JOHN B. HENKELS. 

